Applicants' invention relates to a process for making a folded edge on each side of a flexible sheetlike material prior to having said sheetlike material formed and cured in an oven to give it a rigid form. The folded edge on each side of said sheet actually results in a double thickness of material on each edge. Although not limited to this aspect, applicants have used this invention to provide folded edge sheet material which is used as fill in a cooling tower. Typical application of applicants' process is shown in FIG. 10 where wavelike sheets of fill material are continuously formed. As shown in FIG. 10, the sheets have a double edge and preparing this double edge is the subject matter of applicants' invention.
Applicants have found that folding over a portion of the sheet edge has provided considerably more strength to the sheet than if a raw edge of the sheet were merely coated with a strength forming compound such as a neoprene compound. Furthermore, applicants have found that if the sheetlike material is being used as fill in a cooling tower and if the edges of the sheet were not folded over to provide additional strength and rigidity, the unfolded edge sheet, when placed in an air stream of 500 - 750 feet/minute velocity, is subject to destructive fluttering and vibration. The problem can be partially solved by coating raw edges with a neoprene compound such as described above but this is an expensive and time consuming process. Also, when a sheet having coated edges only is used in longitudinal configuration as cooling tower fill, the strength added by a thin edge coating is negligible over an uncoated sheet.